Unit 3: Chemical Formulas & Equations

EQ: What kind of PRECISE information can a chemical reaction depict for us?

the LANGUAGE of ChEmIsTrY

*  Chemical Symbols: 1,2, or 3 letters that represent an element’s atomic number (specific element) *  we already saw basic symbols -- periodic table & Table s

the LANGUAGE of ChEmIsTrY

*  Diatomic Molecules: *  H O F Br I N Cl = the 7 elements that exist as diatomic

molecules (or Br I N Cl H O F) *  Having 2 atoms of identical elements bonded together *  contain subscripts in their chemical formulas *  ** H2 O2 F2 Br2 I2 N2 Cl2

the LANGUAGE of ChEmIsTrY * Compounds: Tell us both qualitative and

quantitative information via their chemical Formulas

* Qualitative: info not counted or measured,

like what elements are in the compound

* Quantitative: info countable or

measurable like # atoms of each element

in a compound

*  what type of qualitative and quantitative info are

these two chemical formulas depicting?

the LANGUAGE of ChEmIsTrY Types of Formulas: *  1) Empirical à represents the simplest integer ratio

in which atoms combine to form a compound *  **think Least Common Multiple (math) *  i.e. MgCl2 ratio is 1:2, aka 1Mg atom for every 2 Cl atoms

* 2) Molecular à of a molecule (group of bonded

atoms that compose a discrete substance); can be a multiple of the empirical formula *  i.e. Glucose = C6H12O6, which is 6 times the empirical

formula of CH2O

Atoms, Compounds, & Ions

Atoms are electrically ________! J Ions are ________ atoms/particles! à Umm, so tell us something we

don’t know!? LOL

Charges of Ions: (we ALSO know this!) * Metals = (tend to be) POSITIVE (+) * Non-Metals = (tend to be) NEGATIVE (-)

Atoms, Compounds, & Ions

Examples: (what types of ions/charges do these become) * 1) Mg * 2) Al * 3) Cl * 4) P * 5) Rb * 6) S

* Mg2+

* Al3+ * Cl-

* P3- * Rb+

* S2-

ßAtoms Ions à

Polyatomic Ions **Check out Reference table E** * Poly – more than one, ATOMIC – atoms, so group

of atoms bonded together that posses a charge (are IONs) * What about the (parentheses)?!? ** PREVIEW

* ex: (NH4)3PO4 Ammonium Phosphate à locate on table

* THREE NH4+ ions

* ONE PO43- ions

* TOTALS: * 3 N’s & 12 H’s * 1 P & 4 O’s

Coefficients JUST. LIKE. IN. MATH.

WHOAHHHHHH! J * The # in front of a chemical formula * examples: what do these mean? * 2x + 5…. * 5(x2 + 10x – 3)…

* so what do you think THESE mean? * 2H2O * 4Mg(NO3)2

Coefficients How many of each type of atom are in the following molecular compounds?

Ca(NO3)2 3Ca(NO3)2 K3PO4

5K3PO4

* 1 Ca, 2 N’s, & 6 O’s

* 3 Ca’s, 6 N’s & 18 O’s

* 3 K’s, 1 P, & 4 O’s

* 15 K’s, 5 P’s & 20 O’s

Hydrates Water can get bound to an ionic solution, form a crystal lattice with the solution, & then get trapped….aka, a Hydrate. Example: Barium Chloride, BaCl2, traps 2 water molecules, so BaCl2�2H2O

Copper Sulfate, CuSO4 has 5 hydrates, what is it’s molecular formula going to look like?

CuSO4�5H2O

Equalizing Charges – “Matchmaker” Status aka…How to make compounds electrically NEUTRAL: *  1) Identify the POSITIVE ION & CHARGE

ex) Sodium = Na+

* 2) Identify the NEGATIVE ION & CHARGE ex) Chlorine = Cl-

* 3) Balance the CHARGES Na + & Cl – are a 1:1 ratio (1 Positive, 1 Negative) so they are neutral when combined together as NaCl * 4) If the charges are not equal, use the “criss-cross”

method to balance them out… Mg2+ & Cl - … becomes MgCl2 **show on board**

Equalizing Charges – “Matchmaker” Status How do we play matchmaker with these examples?

1) Al & OH à

2) Ca & ClO3 à

3) K & PO4 à

* Al3+ & (OH)- * Al(OH)3

* Ca2+ & ClO3-

* Ca(ClO3)2

* K+ & PO43-

* K3PO4

Naming Compounds (IUPAC) - IONIC * 1) Identify the POSITIVE ION

à usually metallic ex) Na = SODIUM * 2) Identify the NEGATIVE ION

à usually Non-metallic ex) Cl = CHLORINE * 3) Keep the name of the positive ion & change

the name of the negative ion: ex) Chlorine = Chloride

Therefore, our name is Sodium Chloride

(IUPAC) IONIC EXAMPLES How do we name the following example compounds?

1) KCl à

2) MgS à

3) AlNà

* Potassium Chloride

* Magnesium Sulfide

* Aluminum Nitride

Naming Compounds with Polyatomic Ions

* SAME STEPS à some things to take note of: * NAMING: metallic ion + polyatomic

ion * keep BOTH metallic/nonmetallic ion names

ex) KNO3 à Potassium + Nitrate

so NAME = Potassium Nitrate

Naming Compounds with Polyatomic Ions

* *most polyatomic ions are NEGATIVE ions, with important exception = NH4

+ (ammonium) * when combined with a non-metal, the ending

changes to –ide also (just like we do regularly)

* NH4Cl

* NH4NO3

* Ammonium Chloride * Ammonium Nitrate * no change*

the “STOCK SYSTEM”-TRANSITION METALS

* Transition Metals can have more than one common charge

* Ex) Iron à +2 or +3 *  if given Iron Chloride as name, which charge is it?

USE ROMAN NUMERALS * ex) Iron (II) Chloride = Iron +2 oxidation state * Formula? =

* Formula for Iron (III) Chloride = ?

* FeCl2

* FeCl3

ChEMiCaL Reactions & Equations

* Physical Change: change in appearance of substance, NOT the formation of something new

*  ex) Ice melting…

solid à liquid

* Chemical Change: change in identity between REACTANTS & PRODUCTS * Chemical Reactions define

chemical changes

cHeMiCaL Reactions & Equations

Burning of Carbon Dioxide

carbon + oxygen à carbon dioxide

C(s) + O2(g) à CO2(g)

reactants à products

ChEmIcAl Reactions & Equations Endothermic rxns: *  require energy for rxn. to

occcur *  reactants ABSORB

energy *  ex) cooking, ice melting

Exothermic rxns: * RELEASE of

thermal energy during rxn *  ex)burning CO2 ,

freezing of water

Balancing CHeMiCaL Reactions Law of Conservation of Mass: matter is neither created nor destroyed in chemical reactions…aka, numbers & kinds of atoms don’t change

C + O2 à CO2 1 C atom + 2 O atoms à 1 C atom 2 O atoms

H2 + O2 à H2O what’s wrong? we’re missing another Oxygen!

2H2 (g) + O2 (g) à 2H2O (g) 4 H’s, 2 O’s à 4 H’s 2 O’s A Conservation of ATOMS =

BALANCED J -- charge/energy/atoms

Balancing CHeMiCaL Reactions How do we balance POLYATOMIC IONS in reactions??

AgNO3 + MgCl2 à Mg(NO3)2 + AgCl *Q?

2AgNO3 + MgCl2 à Mg(NO3)2 + 2AgCl

Other example: C3H8 (g) + O2 (g) à H2O (g) + CO2 (g) *Q?

C3H8 (g) + 5O2 (g) à 4H2O (g) + 3CO2 (g) #C = 3 à #C = 3 #H = 8 #H = 8 #O = 10 #O = 10

SYNTHESIS REACTION A + B à AB

When two or more reactants combine to form a single product = synthesis, or combination reaction examples: * 2H2(g) + O2(g) à 2H2O(g)…formation of water * 4Fe(s) + 3O2(g) à 2Fe2O3(s)….rusting of iron * CO2(g) + H2O(l) à H2CO3(aq)….involving cmpds

DECOMPOSITION REACTION AB à A + B

When a single compound breaks down into two or more simpler substances = decomposition, or analysis reaction examples: * H2O(l) à H2(g) + O2(g)…decomp of water

* CaCO3(s) à CaO(s) + CO2(g) … 1 cmpd à 2 cmpds

SINGLE REPLACEMENT REACTION A + BX à B + AX

When one element replaces another element in a compound = single replacement reaction example: * Cu(s) + 2AgNO3(aq) à Cu(NO3)2(aq) + 2Ag(s)

(what’s happening)…copper wire put in silver nitrate solution, silver crystals form (solid) on wire and solution becomes blue

SINGLE REPLACEMENT REACTION *  check out TABLE J****Activity Series *  If a METAL or NONMETAL is arranged below

the element in question, then it WILL REACT *  If it is NOT below it, then it WILL NOT replace the

element in the reaction. examples: Zn + Cu(NO3)2 à Cu + Zn(NO3)2 ….WILL REACT Cu + Zn(NO3)2 à No reaction F2 + 2NaCl à Cl2 + 2NaF … WILL REACT Cl2 + NaF à No reaction

DOUBLE REPLACEMENT REACTION AB + CD à AD + CB

When two compounds ‘SWAP’ components = double replacement reaction; usually produce precipitates, a gas, or molecular compound (like water) example: AgNO3(aq) + NaCl(aq) à AgCl(s) + NaNO3(aq) (what’s happening)…silver nitrate and sodium chloride are mixed, and white precipitate of silver nitrate forms (solid) and silver chloride is produced

UNKNOWNS ?? Since LAW of CONSERVATION OF MASS tells us that both sides of a reaction must have equal parts of matter, we can determine what reactants or products are missing from a chemical reaction.

2Na + 2H2O à X + 2NaOH # Na’s = 2 à # Na’s = 2 # H’s = 4 # H’s = 2 # O’s = 2 # O’s = 2

what’s missing?? = H2 = X

UNKNOWNS ?? We can also determine the missing MASSES of each side of our chemical equations: if 103.0 g potassium chlorate are decomposed to form 62.7g of potassium chloride and oxygen gas, how many grams of oxygen are formed? (given equation)

2KClO3 à 2KCl + 3O2 mass KClO3 = 103.0g mass KCl = 62.7g mass O2 = ? *total mass must be equal on both sides, therefore:

103.0g = 62.7g + mass of O2 mass of O2 = 103.0g – 62.7g = 40.3g